1. Field of the Invention
The present invention relates to a method and a device for protecting a product against counterfeiting, having associated with the product a transponder on which at least one unique identifier is stored.
2. Description of the Background Art
In many cases, it is difficult or impossible to distinguish counterfeit products from original products at first glance. Counterfeits inflict losses at unacceptable levels on producers of original products, however. Consequently, there is a desire to identify products or goods in general in such a way that original products can be distinguished quickly and unambiguously from counterfeits in a simple way.
A variety of noncontacting identification systems, or so-called radio frequency identification (RFID) systems, are used to monitor a flow of goods. Such a system typically includes a base station or a reader or reader unit and a plurality of transponders or remote sensors (tags), which are located in the response area of the base station at the same time. The transponders and their transmitting and receiving devices customarily do not have an active transmitter for data transmission to the base station. Non-active transponders are called passive transponders if they do not have their own energy supply, and semi-passive transponders if they have their own energy supply. Passive transponders take the energy they require for their supply from the electromagnetic field emitted by the base station.
In general, something known as backscatter coupling is used to transmit data from a transponder to the base station using UHF or microwaves in the far field of the base station. To this end, the base station emits electromagnetic carrier waves, which the transmitting and receiving device in the transponder modulates, using a modulation method, and reflects appropriately for the data to be transmitted to the base station. The typical modulation methods for this purpose are amplitude modulation, phase modulation and amplitude shift keying (ASK) subcarrier modulation, in which the frequency or the phase position of the subcarrier is changed.
An access control method for transponders is described in the proposed standard ISO/IEC_CD 18000-6C dated Jan. 7, 2005. In this method, the transponder is first selected from among a plurality of transponders in a selection or arbitration process. The selection method described is a stochastic method in the form of a slotted ALOHA method. Such selection methods are described in detail in, for example, the “RFID Handbuch,” a textbook by Klaus Finkenzeller, HANSER Verlag, third edition, 2002, which has been published in English by John Wiley & Sons.
Once the transponder has been selected or isolated, the reader transmits a query to the transponder in the form of a return transmission of a random number previously transmitted by the transponder as part of the arbitration process, whereupon the transponder transmits protocol control bits (PC) and an identifier in the form of an electronic product code (EPC) to the reader. The protocol control bits contain information regarding a physical layer of the transmission path. Among other things, the identifier or the electronic product code EPC reflects a product identified by the transponder. The assignment of the EPC to the identified product is standardized, so that the product can be deduced from knowledge of the EPC.
A plurality of identifiers can be stored on the transponder, such as the EPC, a transponder-specific identifier known as the tag ID, and/or a communications-specific identifier such as a key identification. It is also possible, for example, for a manufacturer to identify his products with a specific manufacturer identifier. However, it is possible to bring counterfeit products on the market as so-called clones of the original product by reading out one or more identifier(s) from a transponder and using these identifier(s) on another transponder to label a product.
In order to be able to distinguish original products from counterfeits using an identifier, a data comparison can be performed using a suitable database. By this means, it is possible to determine whether a transponder-specific identifier issued only once has already been sighted in another location, and/or whether counterfeiting of an item is to be inferred for other reasons, for example on the basis of inconsistencies in its history. In other words, certain indicators are collected as a result of the data comparison that make it possible to infer a counterfeit, but this does not provide protection for the original products. A (global) data comparison and an analysis of the data to ferret out counterfeits is therefore only possible with great effort and expense.
Moreover, a global data comparison results in a conflict of goals: on the one hand the identifier is published as widely as possible so that a clone can be detected as quickly as possible, but on the other hand this wide publication makes it easier to read out the identifier and produce a clone.
In order to prevent a transponder from being used for a clone, it is known to assign to the transponder a unique, transponder-specific identifier at manufacture, which is protected by hardware means against overwriting. A transponder of this nature thus cannot be used for a counterfeit by overwriting the transponder-specific identifier. Nonetheless, transponders that are produced without write protection can still be overwritten in the corresponding memory areas.